Overestimating the Risk of Intravenous Contrast Medium-Induced Nephropathy: A Pitfall in Imaging the Genitourinary System

Preoperative Assessment of Hepatocellular Carcinoma with Split-Bolus Combined Phase Contrast-Enhanced Computed Tomography

Background

The aim of this study was to investigate the feasibility of a split-bolus combined phase contrast-enhanced computed tomography protocol in evaluation of liver vasculature in hepatocellular carcinoma (HCC) patients for the purpose of surgery guidance.

Material/Methods

Two groups of patients were recruited for the study: 24 consecutive cases of HCC who underwent multiphasic CT examination, and 22 consecutive cases who afterwards underwent split-bolus combined phase CT examination. The multiphasic protocol included an unenhanced scan and 3 image acquisitions after contrast injection. The injection of contrast medium was 440 mgI/kg in a single bolus. The split-bolus combined phase protocol included unenhanced scan and combined phase. The injection of contrast medium was 440 mgI/kg for the first bolus and 220 mgI/kg for the second bolus. The vascular delineation was evaluated with Likert scales. The CT values were measured, and the contrast-to-noise ratio (CNR) was calculated. We also compared the effective radiation dose (ED) of the 2 protocols.

Results

All mean CT values were significantly higher in the split-bolus protocol than in the multiphasic protocol (all P<.05), except for the hepatic vein (P>.05). The ED was significantly lower in the split-bolus protocol, corresponding to a dose reduction of 66% compared to the multiphasic protocol (P<.05). The scores of the branches of the hepatic vein in the split-bolus protocol were not lower than those in the multiphasic protocol.

Conclusions

For the preoperative HCC patients, the split-bolus combined phase CT examination meets the diagnostic requirement of surgical planning, with approximately 60% reduction in the radiation dose.

Opportunities for new CT contrast agents to maximize the diagnostic potential of emerging spectral CT technologies

The introduction of spectral CT imaging in the form of fast clinical dual-energy CT enabled contrast material to be differentiated from other radiodense materials, improved lesion detection in contrast-enhanced scans, and changed the way that existing iodine and barium contrast materials are used in clinical practice. More profoundly, spectral CT can differentiate between individual contrast materials that have different reporter elements such that high-resolution CT imaging of multiple contrast agents can be obtained in a single pass of the CT scanner. These spectral CT capabilities would be even more impactful with the development of contrast materials designed to complement the existing clinical iodine- and barium-based agents. New biocompatible high-atomic number contrast materials with different biodistribution and X-ray attenuation properties than existing agents will expand the diagnostic power of spectral CT imaging without penalties in radiation dose or scan time.